The present invention relates to metallurgical processes and more particularly to a method of treating dross materials extracted from melting chambers of metallurgical processes, particularly from those melting chambers utilized to melt and remelt aluminum ore and/or aluminum scrap materials to improve homogeneity with alloying elements being added to further improve physical properties.
It long has been known in the metallurgical arts to mix salt with an aluminum metal or dross material and to melt or remelt the same to provide fused aluminum and fused salt which is continuously circulated in the melting process, attention being directed to U.S. Pat. Nos.: No. 2,987,391, issued Jun. 6, 1961 to T. W. F. Foster et al; to No. 3,070,437, issued Dec. 25, 1962 to Robert W. Bacheldor; and to No. 3,417,166, issued on Dec. 17, 1968 to T. W. F. Foster. In this later, Foster Pat. No. 3,417,166 it also is disclosed to provide a salt composition of sodium chloride and potassium chloride in selected proportions by weight to form an eutectic mixture in the melting of aluminum with the density of the mixture being less than the metal to be melted so that the metal may be collected below the molten salt to be protected from the atmosphere.
It also is known to transport dross materials removed from a melting furnace such as in aluminum melting processes to a heated rotary kiln where the dross materials are again mixed with appropriate salts and a certain amount of aluminum in the dross materials is recaptured from the heated rotary kilns.
Further, it generally is known in the metallurgical arts to suppress and utilize waste materials in the form of metallurgical dusts created by metallurgical furnaces by wetting down such dusts entrained in gaseous by-products with liquids and subsequently treating the wetted dust products for recycling recovery. In this regard, attention is directed to U.S. Pat. No. 3,320,052, issued to J. J. Bowden on May 16, 1967, wherein dust particles entrained in gas formed in an aluminum melting process are wetted down with water and the resulting sludge treated with lime, limestone, iron oxide, mill scale and dolomite to absorb the water, producing a flux utilizable in the steel making process. Attention also is directed to U.S. Pat. No. 3,996,340, issued to F. Steineke on Dec. 7, 1976, wherein silica dust recovered from metallurgical furnace smoke is admixed with fluorspar and treated with steam and aluminum oxide to form aluminum fluoride for use in an aluminum melting process. Such dust suppression with water and steam would be highly undesirable with most dross materials and in many instances could even prove to be calamitous.
The present invention recognizing the need for material and energy conservation in metallurgical melting processes and the further need for environmental control and recovery of certain waste materials resulting from such metallurgical processes provides a unique and novel method for accomplishing the same, the present invention being particularly useful in aluminum melting and remelting operations where dross materials have a course consistency of a porous nature and have a substantial heat. In accordance with the several steps of the present invention, the heat of dross materials recovered from a melting furnace is utilized with a treating agent to substantially reduce process voids and to promptly enhance the function of the treating agent as a dust suppressant which, in turn, enhances pollution control and provides a substantially increased downstream recovery of useful metals with increased metal recoveries of as much as from forty to seventy percent and with a minimal overall amount of undesirable pollutants passed to ambient and to landfill materials. Further, not only are the steps of the present invention economical and straight forward in their execution, requiring a minimum of comparatively economical and unsophisticated equipment in their performance but, in addition, considerable energy is saved both in carrying out the inventive process and in carrying out the downstream metal recovery process which previously required a substantial amount of energy in the form of cooling agents.
Various other features of the present invention will become obvious to one skilled in the art upon reading the disclosure set forth herein.